Conversion Calculators
Free online unit converters. Convert between metric and imperial units for length, weight, temperature, speed, and more.
Length Converter
Convert between meters, feet, inches, miles, and more
Weight Converter
Convert between kg, pounds, ounces, grams, and more
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin
Speed Converter
Convert between mph, km/h, knots, and more
Volume Converter
Convert between liters, gallons, cups, and more
Area Converter
Convert between square feet, square meters, acres
Time Converter
Convert between seconds, minutes, hours, days
Milliseconds Converter
Convert milliseconds to other time units
Data Storage Converter
Convert between bytes, KB, MB, GB, TB
Pressure Converter
Convert between PSI, bar, pascal, atm
Energy Converter
Convert between joules, calories, BTU, kWh
Roman Numeral Converter
Convert between Roman and Arabic numerals
Shoe Size Conversion
Convert international shoe sizes
Understanding Unit Conversions
Metric vs Imperial
The world uses two main measurement systems: the metric system (used by most countries) and the imperial system (used primarily in the United States).
Metric System
- • Based on powers of 10
- • Used by most of the world
- • Units: meter, gram, liter
- • Prefixes: kilo, centi, milli
Imperial System
- • Various conversion factors
- • Used in USA, UK (partially)
- • Units: foot, pound, gallon
- • Historical origins
Common Conversion Quick Reference
| Metric | ≈ | Imperial |
|---|---|---|
| 1 kilometer | = | 0.621 miles |
| 1 meter | = | 3.281 feet |
| 1 centimeter | = | 0.394 inches |
| 1 kilogram | = | 2.205 pounds |
| 1 liter | = | 0.264 gallons (US) |
| 0°C | = | 32°F |
Metric Prefixes
| Prefix | Symbol | Factor | Example |
|---|---|---|---|
| kilo | k | 1,000 | 1 km = 1,000 m |
| hecto | h | 100 | 1 hm = 100 m |
| deca | da | 10 | 1 dam = 10 m |
| (base) | - | 1 | 1 m |
| deci | d | 0.1 | 1 dm = 0.1 m |
| centi | c | 0.01 | 1 cm = 0.01 m |
| milli | m | 0.001 | 1 mm = 0.001 m |